Kava in the Treatment of Generalized Anxiety Disorder

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Abstract

Kava (Piper methysticum) is a plant-based medicine, which has been previously shown to reduce anxiety. To date, however, no placebo-controlled trial assessing kava in the treatment of generalized anxiety disorder (GAD) has been completed. A total of 75 participants with GAD and no comorbid mood disorder were enrolled in a 6-week double-blind trial of an aqueous extract of kava (120/240 mg of kavalactones per day depending on response) versus placebo. γ-Aminobutyric acid (GABA) and noradrenaline transporter polymorphisms were also analyzed as potential pharmacogenetic markers of response. Reduction in anxiety was measured using the Hamilton Anxiety Rating Scale (HAMA) as the primary outcome. Intention-to-treat analysis was performed on 58 participants who met inclusion criteria after an initial 1 week placebo run-in phase. Results revealed a significant reduction in anxiety for the kava group compared with the placebo group with a moderate effect size (P = 0.046, Cohen d = 0.62). Among participants with moderate to severe Diagnostic and Statistical Manual of Mental Disorders-diagnosed GAD, this effect was larger (P = 0.02; d = 0.82). At conclusion of the controlled phase, 26% of the kava group were classified as remitted (HAMA ≤ 7) compared with 6% of the placebo group (P = 0.04). Within the kava group, GABA transporter polymorphisms rs2601126 (P = 0.021) and rs2697153 (P = 0.046) were associated with HAMA reduction. Kava was well tolerated, and aside from more headaches reported in the kava group (P = 0.05), no other significant differences between groups occurred for any other adverse effects, nor for liver function tests. Standardized kava may be a moderately effective short-term option for the treatment of GAD. Furthermore, specific GABA transporter polymorphisms appear to potentially modify anxiolytic response to kava.

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Most cited references 23

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An effect-size analysis of pharmacologic treatments for generalized anxiety disorder.

Marta Hidalgo, Jonathan Davidson, L Tupler (2007)

Generalized anxiety disorder (GAD) is a prevalent and impairing disorder, associated with extensive psychiatric and medical comorbidity and usually characterized by a chronic course. Different drugs have been investigated in GAD; among them are the following: 1) SSRIs: paroxetine, sertraline, fluvoxamine and escitalopram; 2) SNRI1s: venlafaxine; 3) benzodiazepines (BZs): alprazolam, diazepam and lorazepam; 4) azapirones (AZAs): buspirone; 5) antihistamines (AHs): hydroxyzine; 6) pregabalin (PGB); and 7) complementary/alternative medicine (CAM): kava-kava and homeopathic preparation. We conducted an effect size (ES) analysis of 21 double-blind placebo-controlled trials of medications treating DSM-III-R, DSM-IV or ICD-10 GAD using HAM-A change in score from baseline or endpoint score as the main efficacy measure. Literature search was performed using MEDLINE and PsycINFO databases including articles published between 1987 and 2003 and personal communications with investigators and sponsors. comparing all drugs versus placebo, the ES was 0.39. Mean ESs, excluding children, were PGB: 0.50, AH: 0.45, SNRI: 0.42, BZ: 0.38, SSRI: 0.36, AZA: 0.17 and CAM: -0.31. Comparing ES for adults versus children/adolescents (excluding CAM) and conventional drugs versus CAM (excluding children/adolescents) we found significantly higher ES for children/adolescents and for conventional drugs (p < 0.001 and p < 0.01, respectively). No significant differences were found when comparing date of publication, location of site (i.e. US versus other), fixed versus flexible dosing, number of study arms, or number of outcome measures used. Medications varied in the magnitude of their ES, ranging from moderate to poor. Adolescents and children showed a much greater ES compared with adults. Subjects taking CAM had worse outcomes than placebo.

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A randomized, double-blind, placebo-controlled trial of oral Matricaria recutita (chamomile) extract therapy for generalized anxiety disorder.

K Rockwell, Jun Mao, Irene Soeller … (2009)

We conducted a randomized, double-blind, placebo-controlled efficacy and tolerability trial of Matricaria recutita (chamomile) extract therapy in patients with mild to moderate generalized anxiety disorder (GAD). We hypothesized that chamomile would be superior to placebo in reducing GAD symptoms with a comparable tolerability profile. Sixty-one outpatients with mild to moderate GAD were enrolled, and 57 were randomized to either double-blind chamomile extract (n = 28) or placebo therapy (n = 29) for 8 weeks. The study was powered to detect a statistically significant and clinically meaningful group difference in change over time in total Hamilton Anxiety Rating (HAM-A) scores. Secondary outcomes included change in the Beck Anxiety Inventory, Psychological Well Being, and Clinical Global Impression Severity scores and the proportion of patients with 50% reduction or more in baseline HAM-A score. We observed a significantly greater reduction in mean total HAM-A score during chamomile versus placebo therapy (P = 0.047). Although the study was not powered to identify small to moderate differences in secondary outcomes, we observed a positive change in all secondary outcomes in the same direction as the primary outcome measure. One patient in each treatment group discontinued therapy for adverse events. The proportion of patients experiencing 0, 1, 2, or 3 adverse events or more was not significantly different between groups (P = 0.417). This is the first controlled clinical trial of chamomile extract for GAD. The results suggest that chamomile may have modest anxiolytic activity in patients with mild to moderate GAD. Future studies are needed to replicate these observations.

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Kava kava: examining new reports of toxicity.

Dallas Clouatre (2004)

Before 1998, extracts of kava kava, Piper methysticum, were considered to be very safe alternatives to anxiolytic drugs and to possibly exert a wide range of other benefits. Major reviews published through the end of 2002 continued to confirm kava's safety and efficacy. Nevertheless, by January 2003 kava extracts had been banned in the entire European Union and Canada, and were subject to cautions and advisories by the US FDA as a result of 11 cases of hepatic failure leading to liver transplants, including four deaths. A total of 78 cases of hepatotoxicity reputedly linked to kava ingestion are available for review from various databases. Of these adverse events, four probably are linked to kavalactones taken alone and another 23 are potentially linked to kava intake, but also involve the concomitant ingestion of other compounds with potential hepatotoxicity. Three possible mechanisms for kavalactone hepatotoxicity are known: inhibition of cytochrome P450, reduction in liver glutathione content and, more remotely, inhibition of cyclooxygenase enzyme activity. The direct toxicity of kava extracts is quite small under any analysis, yet the potential for drug interactions and/or the potentiation of the toxicity of other compounds is large. Presently, kava toxicity appears to be "idiosyncratic." The risk-to-benefit ratio of kava extracts, nevertheless, remains good in comparison with that of other drugs used to treat anxiety.